EVOTOMYS 267 



No single essential character and no combination of characters 

 can be cited as serving to distinguish all forms of E. gapperi from 

 all forms of E. glareolus. The American species and all its 

 geographical races might very well be treated as so many additional 

 subspecies of E. glareolns. But since in most forms of E. gapperi 

 the tail is relatively shorter, the hind-foot absolutely longer, and 

 Hi' often more complex than is usual in E. glareolus, we may take 

 these average differences, coupled with the geographical distinction 

 as sufficient to justify specific separation. 



A considerable number of more or less well-marked subspecies 

 of E. gapperi are now recognized and the descriptions given of 

 them are summarized below. 



28a. Evotomys gapperi gapperi Vigors. 



1830. Arvicola gapperi Vigors, Zool. Journ., 5, p. 204. 



1857. Arvicola (Hypudceus) gapperi Baird, Mamm. N. Amer., p. 518. 



1877. Evotomys rulilus Coues, Men. N. Amer. Rodentia, Muridae, 



p. 136 (in part). 

 1885. Evotomys rutilus gapperi True, Proc. U.S. Nat. Mus., 7, p. 596. 

 1891. Evotomys gapperi Merriam, N. Amer. Fauna, No. 5, p. 119; 



Bailey, Proc. Biol. Sec. Washington, 11, p. 122, 1897. 

 1894. Evotomys fuscodorsalis Allen, Bull. Amer. Mus. N.H., 6, p. 103; 



described from Trousers Lake, New Brunswick, Canada; type : 



Am. Mus. N.H. No. g-llf^ adult male. 

 1912. Evotomys gapperi gapperi Miller, "List," p. 210; "List," 1924, 



p. 402. 



Type. — Unknown. 



Type locality. — Between York and Lake Simcoe, Ontario, 

 Canada. 



Range. — From Massachusetts, New Jersey, and Pennsylvania 

 northward and from the Atlantic coast westward to the Rocky 

 Mountains in Canada. 



Characters. — Size medium, hind-foot about 18 mm. ; condylo- 

 basal length of skull to 24'2 mm. 



Mantle in winter bright chestnut, with numerous black hairs 

 aud a slight frosting produced by the white subterminal bands of 

 the rufous-tipped hairs. Sides bright buffy ochraceous. Under 

 parts washed with pale buff. Hands and feet silvery grey. Tail 

 scarcely more than twice the length of the hind-foot, about 38% 

 of the length of the head and body, bicoloured, brownish above, 

 becoming black at the tip, greyish-buff to the tip below. 



In high pelage, a rufous stripe extends across the orbit to black 

 spot at base of mustache on each side. Colour in summer darker, 

 the feet and tail more dusky. 



Skull essentially as in Evotomys glareolus. Comparing the 

 large series in the British Museum (mainly in the Miller Collection) 

 with skulls of E. g. hritannicus, I can detect no tangible differences 

 by mere inspection. Careful measurement of a series of old, and 

 therefore fully developed, skulls of the two forms show that in 

 E. g. gapperi the zygomatic breadth is a little less, the width of the 



